The number one question we hear from homeowners considering microcement in Los Angeles is some version of the same concern: will it crack? It's a fair question. Microcement is a thin-layer material applied over existing substrates — and if you've seen a failed installation, the cracks can be jarring. But here's the truth that most people don't know: microcement almost never fails on its own. When cracks appear, the cause is almost always incorrect installation process, wrong materials for the substrate, or skipped steps. Follow the right process with the right materials and cracks simply don't happen.
This guide breaks down the three most common microcement applications — interior walls on drywall, shower enclosures on cement board or floated walls, and floors — and explains the exact installation process for each one. Understand what correct installation looks like and you'll understand exactly why properly done microcement lasts for decades without a single crack.
The Most Common Concerns — And the Real Answer
Before getting into the installation specifics, it's worth addressing the most common worries we hear directly. Every single one of them has a definitive answer rooted in process and materials — not in any inherent weakness of microcement as a material.
Will it crack at the drywall seams? Only if the seams weren't properly reinforced before application. Mesh tape embedded in the base coat eliminates this completely.
Will it crack in the shower from water and steam? Only if applied over the wrong substrate or without the correct waterproofing membrane. Applied correctly over cement board with a crystalline waterproofing system, it performs indefinitely.
Will it crack on the floor from foot traffic and furniture? Only if the subfloor wasn't properly prepared or if the wrong product was specified. The right floor-rated microcement, applied over a structurally sound substrate, handles normal residential and even commercial traffic without issue.
Will it crack as the house settles? Correctly applied microcement has enough flexibility in its polymer matrix to move with normal building movement. Rigid application on a moving substrate without proper priming is where this problem originates.
Will it stain or discolor in the kitchen or bathroom? Only if the wrong sealer was used or the surface wasn't sealed properly. The correct two-component polyurethane or epoxy sealer makes the surface non-porous and resistant to oil, water, and most household cleaners.
The bottom line
Every concern about microcement has a solution that is already built into the correct installation process. The material doesn't fail — the process fails. Which is why choosing a contractor who knows the process is the most important decision you'll make.
Applying microcement directly to drywall is the most common wall application in Los Angeles residential projects — and it's the one where corners are most often cut. The drywall substrate is forgiving enough that shortcuts can look fine for a few weeks before the cracks appear at the seams or corners. Here's why that happens and exactly how to prevent it.
Why walls crack — the real causes
Drywall is made of gypsum panels joined at seams. Those seams move. Temperature changes, humidity shifts, and normal building movement cause the panels to expand, contract, and flex slightly — and if the microcement layer isn't properly bridged across those seams, it cracks right along them. The other common crack source on walls is corners — both inside corners where two walls meet and outside corners where the drywall edge is exposed and vulnerable.
What goes wrong
Skipping mesh reinforcement at seams and corners. Applying microcement directly over unprepared or unsealed drywall. Using the wrong primer — or no primer at all. Any one of these shortcuts guarantees cracks within weeks or months.
The correct installation process — drywall walls
1
Inspect and prepare the drywall
All existing drywall seams must be taped and mudded flush. Any screws or fasteners must be countersunk and filled. Damaged sections must be repaired and sanded flat. The surface needs to be structurally sound, dry, and free of dust, grease, or paint that hasn't fully cured. This step is non-negotiable — microcement reveals every imperfection.
2
Apply a sealing primer
Bare drywall is porous and will absorb the microcement base coat unevenly, causing color variations and adhesion failures. A penetrating primer seals the surface and creates a uniform, consistent base for the microcement to bond to. The primer must be completely dry — typically 24 hours minimum — before any microcement is applied.
3
Embed fiberglass mesh at all seams and corners
This is the most critical step for crack prevention. Alkali-resistant fiberglass mesh tape is applied over every drywall seam, every inside corner, and every outside corner — embedded into the first layer of microcement base coat while it's still wet. The mesh bridges the joint and distributes any movement across a wide area rather than concentrating stress at a single line. No mesh means no bridge means cracks at the seams. It's that simple.
4
Apply first base coat and allow to cure
The first base coat is applied by trowel at approximately 1–1.5mm thickness across the entire surface, embedding the mesh as it goes. This coat establishes the bond to the substrate and begins building the microcement film. It must cure fully — typically 24 hours — before the next coat. Rushing this step causes delamination.
5
Apply second base coat and sand
The second coat builds additional thickness and begins to create the smooth, even surface that the finish coat will be applied over. Once cured, the surface is lightly sanded to remove any trowel marks or high spots. The surface at this stage should feel flat, consistent, and even.
6
Apply finish coat
The finish coat is applied in one or two thin passes — this is where the final color, texture, and aesthetic of the surface is established. The applicator's skill is most visible here. Even trowel pressure, consistent technique, and an eye for the surface are what separate a beautiful finish from a patchy one. The finish coat must cure completely before any sealing begins.
7
Seal with two coats of polyurethane
For interior dry walls, a matte or satin water-based polyurethane sealer is applied in two coats. The sealer closes the surface pores, protects against scuffs and cleaning products, and locks in the color. The first coat is applied, allowed to dry fully, lightly abraded if needed, then the second coat is applied. The surface is ready for use after the sealer has cured — typically 48–72 hours after the final coat.
Result when done correctly
A microcement wall applied to drywall following this process will not crack at the seams, will not crack at the corners, and will maintain its appearance for years with nothing more than normal cleaning. The fiberglass mesh absorbs all substrate movement. The sealer protects the surface. There is no weak point in the system.
Showers are where microcement gets its most demanding test — and where the most spectacular failures happen when the process isn't followed correctly. Continuous water exposure, steam, temperature cycling between hot and cold, and the mechanical stress of cleaning all combine to create conditions that will find any weakness in the system. But when the installation is done right, microcement in a shower is one of the most beautiful and durable finishes available anywhere.
The fundamental difference between a dry wall application and a shower application is the substrate and the waterproofing system. Drywall is not acceptable in a shower under any circumstances — it will absorb moisture, swell, and fail, taking the microcement with it. The correct substrate for a microcement shower is either cement board or a properly floated concrete wall, both of which are dimensionally stable in wet conditions.
Why shower microcement fails — the real causes
The failures we've seen in Los Angeles microcement showers almost all trace back to one of four mistakes: wrong substrate (regular drywall instead of cement board), no waterproofing membrane before the microcement, wrong product (wall-rated instead of wet-area-rated microcement), or inadequate sealing. Any one of these is enough to cause failure. All four together is a disaster waiting to happen.
What goes wrong
Applying microcement over standard drywall in a shower. Skipping the waterproofing membrane. Using a wall-rated microcement product instead of a wet-area system. Applying only one coat of sealer when two or three are required. These mistakes cause delamination, cracking, mold growth behind the surface, and complete system failure.
The correct installation process — showers and wet areas
1
Install cement board substrate
All shower walls must be built on cement board — never standard drywall or green board. Cement board is dimensionally stable when wet and provides a rigid, non-absorbing base that the microcement system can bond to permanently. Boards are installed with cement board screws at the correct spacing, and all joints must be offset from any corners. The cement board itself must be flat — any high spots or lips at the joints must be ground flush before proceeding.
2
Apply waterproofing membrane
This is the step that is most commonly skipped — and the most critical. A crystalline waterproofing membrane or a sheet-applied waterproofing system is applied over the entire shower surface including walls, floor, and the transition to the shower pan, before any microcement goes on. The membrane creates a complete water barrier at the substrate level — so even if any moisture ever penetrates the microcement and sealer, it cannot reach the structure behind. Without this membrane, the microcement sealer is your only waterproofing layer, and sealers are maintenance items that wear over time.
3
Tape and fill all cement board joints and corners
Alkali-resistant fiberglass mesh tape is embedded in waterproofing compound at every joint and every inside and outside corner. This bridges the movement between boards and creates a continuous, flexible, waterproof surface for the microcement to bond to. Corners get a generous application — they are the highest-stress zones in a shower and the most common place for cracks to initiate if this step is rushed.
4
Apply wet-area primer
A primer formulated specifically for wet-area microcement systems is applied over the prepared surface. Wet-area primers have different chemistry from dry-area primers — they create a bond that remains stable under continuous moisture exposure. The primer must cover every square inch of the surface uniformly and must cure fully before microcement application begins.
5
Apply first and second microcement base coats
Two full base coats of wet-area rated microcement are applied, each allowed to cure fully between applications. The base coats build the thickness of the system and create the structural film that the finish coat sits on. Between coats, the surface is inspected for any pinholes, uneven areas, or transitions at the joints — any issues are addressed before moving forward. Wet-area microcement formulations have higher polymer content than standard microcement, giving them the flexibility to handle the thermal cycling of a hot shower without cracking.
6
Apply finish coat
The finish coat establishes the final aesthetic — color, texture, and surface quality. In a shower, this coat is applied with particular attention to consistency, because the surface will be viewed at close range and in varying light conditions. The finish coat must be pinhole-free — any pinholes are entry points for moisture. The surface is inspected carefully before sealing.
7
Apply minimum three coats of wet-area sealer
A wet-area rated two-component polyurethane or epoxy sealer is applied in a minimum of three coats — more than the two used in dry areas. Each coat is allowed to cure fully between applications. The sealer closes every pore in the microcement surface and creates the water-barrier layer at the surface level that works in conjunction with the waterproofing membrane behind the substrate. Three coats is the minimum — some installers apply four for shower floors where the demand is highest.
8
Full cure before first use
A properly installed microcement shower must be allowed to cure fully before the first use — a minimum of 72 hours after the final sealer coat, ideally 5–7 days. Using the shower before full cure is complete is one of the most common causes of early sealer failure. The sealer must be completely hardened before it encounters water, steam, and cleaning products.
Result when done correctly
A microcement shower built on cement board with a proper waterproofing membrane, wet-area rated product, and three coats of wet-area sealer will perform for years without cracking, delaminating, or showing moisture damage. The waterproofing is redundant — two complete barriers between the water and the structure. This is how every microcement shower in Los Angeles should be built.
Floors are the most demanding microcement application — they carry weight, they flex when walked on, they take impact, and they are cleaned more frequently and more aggressively than walls. They also have the most substrate variability — microcement floors in Los Angeles are applied over concrete slabs, wood subfloors, existing tile, and existing hardwood, each of which behaves differently and requires specific preparation.
Why floors crack — the real causes
Floor cracks are almost always substrate problems. A concrete slab that has hairline cracks which weren't bridged before application. A wood subfloor with deflection — flex between the joists — that the microcement layer can't accommodate. Existing tile with hollow spots that create point loads. Or simply a floor-rated microcement applied too thin, without the correct number of coats, over a substrate that wasn't properly prepared.
Important note on wood subfloors
Wood subfloors move — they flex with foot traffic and expand and contract seasonally with humidity. Microcement applied over a wood subfloor requires a flexible primer system and a microcement formulation with high polymer content specifically designed for moving substrates. Standard microcement on a wood subfloor without the correct product will crack. The right product won't.
The correct installation process — floors
1
Assess and prepare the substrate thoroughly
The substrate assessment for floors is more rigorous than for walls. Concrete slabs are checked for cracks, moisture content, and surface hardness. Any existing cracks are routed and filled with flexible epoxy filler before proceeding — microcement will telegraph every crack in the slab below if they aren't addressed. Wood subfloors are checked for deflection — any boards that flex more than L/360 under load need to be stiffened or the substrate needs to be upgraded before microcement can be applied. Existing tile is checked for hollow spots — any loose tiles are removed and replaced, and the grout lines may need to be filled and leveled.
2
Apply crack isolation membrane where needed
For concrete slabs with existing hairline cracks or for wood subfloors, a crack isolation membrane is applied before priming. This uncouples the microcement layer from the substrate movement below — the substrate can move slightly without transmitting that movement as stress into the microcement film above. This is a critical step that is often skipped by inexperienced installers.
3
Apply floor-rated primer
Floor primers are formulated differently from wall primers — they must create a bond strong enough to withstand the shear forces of foot traffic and cleaning. The primer is applied to the entire floor surface and must cure fully. For wood subfloors, a flexible epoxy primer is often specified to accommodate movement.
4
Apply fiberglass mesh over joints and transitions
At any joint in the substrate — expansion joints in a concrete slab, the seam between two sheets of plywood subfloor, or the transition between tile and another substrate — fiberglass mesh is embedded in the first base coat. These are the highest-risk locations for floor cracks and the mesh bridges them completely.
5
Apply two full base coats, sanding between
Floor base coats are applied slightly thicker than wall coats — floors need more film thickness to handle the mechanical demands. Two full base coats are applied, each cured and lightly sanded before the next. The surface between coats is checked for flatness — any high spots, ridges, or transitions are sanded flush. The floor at this stage should feel smooth and even underfoot.
6
Apply finish coat
The finish coat on a floor is applied with attention to both aesthetics and surface consistency. Floor finish coats are often applied with a more aggressive trowel technique than walls, which can create directional texture — this needs to be consistent across the entire surface. The finish coat is inspected carefully for any pinholes before sealing.
7
Apply minimum three coats of floor-rated sealer
Floor sealers must be harder and more abrasion-resistant than wall sealers. A two-component polyurethane floor sealer is applied in a minimum of three coats — some high-traffic areas get four. Each coat must cure between applications. The sealer is the floor's primary defense against staining, abrasion, and moisture, and on a floor it works harder than anywhere else. Don't let any contractor apply fewer than three coats on a microcement floor.
8
Full cure before foot traffic or furniture
Microcement floors must cure fully before any foot traffic, furniture placement, or cleaning. Light foot traffic (socks only, no shoes, no furniture) is acceptable after 48 hours. Full use — shoes, furniture, normal cleaning — should wait a minimum of 7 days. Placing furniture on a microcement floor before full cure leaves permanent impressions in the sealer.
Result when done correctly
A microcement floor installed following this process will not crack at substrate joints, will not show telegraph cracks from the slab below, and will handle normal residential traffic for years. The crack isolation membrane decouples the substrate from the finish. The fiberglass mesh bridges every joint. The three-coat sealer creates a surface hard enough to handle daily life.
The Question to Ask Every Microcement Contractor
Now that you understand what correct installation looks like, you have a powerful tool when evaluating contractors. Ask them directly: walk me through your installation process step by step. A contractor who knows what they're doing will describe something close to what you've read above. A contractor who cuts corners will describe a simpler, faster process — and that simpler process is the reason microcement gets a bad reputation it doesn't deserve.
Specifically ask about fiberglass mesh — do they use it, where, and how? Ask about their waterproofing system for showers. Ask how many sealer coats they apply and what product they use. Ask how long they wait between coats and before the surface can be used. The answers will tell you everything about the quality of the installation you're going to get.
Microcement done correctly is one of the most beautiful, durable, and low-maintenance finishes available. It lasts decades. It doesn't crack. It doesn't peel. It ages with dignity and looks better in a well-lived-in space than almost any other finish material. The difference between that result and a cracked, failed installation isn't the material — it's the process and the hands that execute it.
Every microcement project we do at LA Microcement follows the processes described in this guide. If you have questions about a specific application or substrate situation, we're always happy to walk through it with you before any commitment is made.